In recent years, in the prevailing trend toward a decrease in the size of electrical and electronic equipment, the flow of electric current having higher frequencies through circuits thereof, and the application of higher electric current thereto, not only the electrical and electronic equipment but also components of the magnetic core are required to follow the trend in the production thereof. But the characteristic of a ferrite material which presently prevails reaches the limit. Consequently new materials for the magnetic core are being searched for. For example, the ferrite material is being replaced with compressed magnetic materials such as sendusts, amorphous materials, and an amorphous foil band. But the compressed magnetic materials have a poor moldability and a low mechanical strength after they are fired. The production cost of the amorphous foil band is high because it is produced through a winding process, a cutting process, and a gap forming process. For this reason, practical applications of these magnetic materials have been delayed.
To produce components of the magnetic core which have a configuration variation and characteristics, are compact, and are inexpensive by using magnetic powders having a low moldability, the present applicant proposed a method including the step of coating the magnetic powders contained in the resin composition to be injection-molded with an insulation material and the step of forming the compressed powder magnetic body or the compressed powder magnet in the resin composition by insert molding, and the step of obtaining the components of the magnetic core having a predetermined magnetic characteristic by injection molding. The compressed powder magnetic body or the compressed powder magnet contains a binding agent having a melting point lower than an injection molding temperature. The present applicant obtained a patent for the invention (patent document 1).
An electromagnetic equipment, for a noise filter, which has a composite magnetic core using an amorphous magnetic thin belt as its magnetic core is known. Description is made in the patent specification that the electromagnetic equipment for the noise filter is capable of securing insulation between the winding and the magnetic core and preventing the amorphous magnetic thin band from being cracked and chipped by an external force and the magnetic characteristic thereof from changing. The composite magnetic core of the electromagnetic equipment is constructed of the flanged tubular ferrite magnetic core having the flange at both ends thereof and of the amorphous magnetic thin belt wound around the tubular portion of the ferrite magnetic core within the range not exceeding the height of the flanges. The toroidal coil is wound around the composite magnetic core (patent document 2).
As a composite core material which restrains the level of heat generated owing to an eddy current from increasing from the level of the heat generated by a magnetic core consisting of a compressed powder compact, achieves a high magnetic permeability, has a high strength, and is applicable to use where a vibration and a stress are applied, the proposed composite magnetic material consists of the laminate of the layer of the compressed powder compact formed by coating the surfaces of the powder particles of the magnetic material with the insulating substance and by compression-molding the powders with the powders being electrically insulated and the layer of the rolled magnetic material different from the above-described one (patent document 3).